Channel providers now offer ever increasing number of channels in addition to high definition (HD), on demand choices and high-speed data services. In traditional systems, every service (excluding Video on Demand) is always available for its subscribers regardless of whether someone is watching it. However, making all these types of content and services available requires an enormous amount of bandwidth.
This is partially overcome by channel providers developing switched digital video technology (SDV), which delivers digital video in a more bandwidth-efficient way. For example, in a household where users are watching N different channels at the same time and where there is overlap among the channels that are being watched at particular times (a rule of thumb is that 80% of the users watch 20% of the content), bandwidth is saved by transmitting only the channels that are actually being watched which, in effect, provides a continuous video-on-demand system. Rarely all available channels are watched at the same time by a group of users, so by transmitting only the channels that are being watched, bandwidth can be reused to offer more services.
US 2008/0229379 describes a specific implementing action of channel change requests in an SDV system.
Essentially, SDV works based on the assumption that most viewers will watch the most popular channels most of the time and that niche content is rarely accessed. While this assumption is true for real users, it does not hold for digital video recorders (DVRs) that acquire content on behalf of the user, based on automatic recommendation technology and user preferences. In the case of DVRs, it is not feasible to exclude a large number of TV channels from being delivered since the recording requests from DVRs require a more varied choice of channels to be delivered at the same time. This requires much higher bandwidth, which for some channel providers is impossible.